The application of CRTA and linear heating thermoanalytical techniques to the study of supported cobalt oxide methane combustion catalysts

Two combined thermal analysis-mass spectrometry techniques have been used to ascertain the effects of various support materials on the preparation and subsequent combustion activity of supported cobalt oxide catalysts. Both techniques used small sample masses in order to minimise temperature and pressure gradients throughout the sample during reaction as the sample temperature was increased at a linear heating rate. Temperature-programmed reduction (TPR) techniques employed not only reveal reduction, but also distinguish it from the adsorption (or evolution) of the H2 and the loss of absorbed water. The thermally induced decomposition of supported and unsupported cobalt nitrate hexahydrate was studied using a solid insertion probe mass spectrometer (SIP-MS) system operating under high vacuum. The support material was found to affect the decomposition process significantly. In particular, the decomposition of cobalt nitrate dispersed on γ-Al2O3 occurred via a markedly altered process in comparison with the unsupported nitrate. The ZrO2 and CeO2 supports both exhibited less pronounced effects on the decomposition process. After calcination of dispersed cobalt nitrate species, methane combustion activity was found to be much lower for alumina-supported samples relative to the other supports used. A combined temperature-programmed reduction–mass spectrometry (TPR–MS) technique was used to elucidate a correlation between catalyst activity and reducibility. The reduction of a Co3O4/CeO2 catalyst was also studied under constant rate thermal analysis (CRTA) conditions.